FIELD OF THE INVENTION
The present invention relates to a freight car truck, and in particular to the pedestal area where the axle and bearing are loosely journaled to the side frame.
A common phenomenon with railcar trucks is referred to as truck hunting, which is a swiveling action of the truck while running down the track. Hunting is a consequence of the evolution of the friction bearings being replaced by roller bearings, the latter reducing the axial movements of the wheel set, and also a consequence of increased operating speeds.
With reduced lateral movement in the wheel set, contact to the side frame thrust lugs is achieved quickly, and the resulting force is transmitted through the side frame to the bolster and then to the car body. Excessive hunting causes high lateral accelerations creating wear to the truck components as well as the track. The foregoing is also a cause of lading damage.
There have been attempts at increasing the lateral movement of the wheel set relative to the side frame through the use of elastomeric shear pads in the pedestal area and increased openings in the thrust lug area. Such an approach is disclosed in Jones U.S. Pat. No. 3,381,629. However, the foregoing known approach has not been successful.
The present invention comprises use of an adapter and adapter pad which can slip, allowing the wheel set lateral movement without contact to the side frame, thereby lessening the damaging forces, while still achieving running speeds which may approach 80 miles per hour, a substantial increase over conventional railcars. Another advantage of the present invention is that it precludes the need for constant contact side bearings, thereby affording initial savings and reduced maintenance.
Brodeur et al. U.S. Pat. No. 3,844,226 discloses an arrangement where the two wheels, the axle and the bearings, which are fixed to one another, can move laterally relative to the side frame. At column 2, line 32, there is a reference to a total lateral movement of 3/4 inch, although there is no disclosure as to how the components would have to be modified to achieve such a magnitude of lateral movement. Furthermore, Brodeur et al. discloses a non-metallic plate 30 which would not hold up well in use and would be subject to deterioration in a relatively short time.
A preferred embodiment of the present invention includes both a wear plate or pedestal liner which mounts under the pedestal portion of the side frame, and also an adapter plate which mounts over the top of the bearing adapter. A special adapter pad is mounted either on the underside of the pedestal liner or on the top of the adapter plate.
Wear plates or pedestal liners per se are known in the art and are disclosed in U.S. Pat. Nos. 3,897,736 and 4,230,371. However, the foregoing prior art patents do not teach use of the adapter plate or the adapter pad of the present invention. The present invention further includes application of a novel low friction coating to the bottom of the wear plate or pedestal liner.
Jones U.S. Pat. No. 3,381,629 is relevant to the extent that it teaches lateral movement between the wheel set and bearing on the one hand and the side frame. FIG. 2 of the Jones patent shows an upper steel plate 32, a rubber pad 30, and a lower steel plate 33. Jones shows a side frame in FIG. 3 having ribs at 36 and 37. While there is limited clearance between the ribs 36 and 37, and the upper steel plate 32, such clearance is limited and does not afford meaningful lateral movement.
Jones discloses an assembly where lateral movement is permitted, but in a manner totally different from our present invention. Jones provides lateral movement due to deformation or shearing of the rubber pad 30. One of the problems with the Jones structure is that when the robber pad deforms or shears laterally in one direction, it will tend to bounce back or rebound in a somewhat violent manner, which can cause significant wear to the side frame, bolster and other components as well as resultant deterioration of the quality of the car ride.
Still referring to the above Jones patent, FIG. 5 shows the manner in which lateral movement is limited. A portion of the side frame is shown at 52, and it fits into an opening between opposed shoulders 56 of an adapter. Spaces are shown at 53 and 54 which define the amount of lateral movement permitted between the wheel set and adapter on the one hand and the side frame. In FIG. 5 of the Jones patent, the space between the adapter shoulders 56 is standard, but Jones modifies the side frame to make the member 52 narrower than in a standard side frame, and in this manner Jones permits the relative lateral movement discussed above, under the control of the deformable rubber pad 30.
Thus, in conventional truck assemblies, there is no lateral movement, and any spaces as shown at 53 and 54 in FIG. 5 of Jones would be nominal, and not sufficient to permit meaningful lateral movement. Jones thus modified the side frame and reduced the width of the member 52 to make relative lateral movement possible.
In a preferred embodiment of the present invention, a standard side frame is used, meaning that the standard width of the side frame member shown at 52 in Jones is not reduced. Instead, the present invention involves opening up the space between the shoulders or lugs shown at 56 in FIG. 5 of the Jones patent.
Specifically, it is a feature of the present invention to increase the standard distance between those adapter shoulders 56 by an amount approximately equal to 3/4 inch. For example, the preferred distance between those shoulders 56 is approximately 4 and 9/16 inches, which is 3/4 inch greater than standard, thereby permitting relative lateral movement between the wheel set and the side frame of approximately 3/4 inch.
The foregoing objects and advantages of the invention will be apparent from the following description of certain preferred embodiments thereof, taken in conjunction with the accompanying drawings.